(1) Field of the Invention
The present invention relates to a method for separating a liquid mixture by using a membrane. More particularly, the present invention relates to a method for separating a liquid mixture, in which an intended component in the liquid mixture is concentrated in the interiors of particles and the particles are then separated by a polymeric porous membrane while transporting the particles under an electrostatic field.
(2) Description of the Related Art
In order to separate a mixture of components having close boiling points or an azeotropic mixture by distillation, it is necessary to repeat distillation several times or carry out azeotropic distillation, and hence, a large quantity of energy is necessary. Reduced pressure distillation or steam distillation is utilized for separating a component which is easily decomposed at a high temperature close to the boiling point. In this case, however, required energy is larger than that in normal pressure distillation. Accordingly, development of a technique of separating a liquid mixture, that can replace the distillation method, is eagerly desired and at the present, a separating method using a membrane attracts attention in the art.
In existing separating techniques using a membrane, a high separating property and a high permeability are not compatible with each other. Namely, if the separating property is high, the permeability is low, or if the permeability is high, the separating property is low. Thus, a separating technique using a membrane, which has a high separating property and a high permeability, has not been developed. Therefore, in the actual operation, the membrane thickness is reduced to increase the permeation of the liquid through the membrane, or the number of the membrane stages is increased to compensate a poor selectivity. However, the former method has a problem in that the strength of the membrane is insufficient, and the latter method has a problem in that the apparatus becomes complicated.